Hi, wondering if anyone can shed some light on something I observed over the last few days while testing H2 on haproxy 1.8, 2.0 ,2.2 and 2.3. I ended up with a number of fe,be configurations trying out different scenarios, however tested them all respectively against each version mentioned.
The test was a curl agent with the same request going in a fe out to the same be. The be was an nginx ingress controller with mostly default config and the request contained a ~5k (oauth) cookie, this cookie was causing the issue. If I went a byte >4096 the connection crashed out. This got resolved on the ingress controller and as far as I can see isn’t a bug with haproxy, however I can’t be sure because I wouldn’t expect the results below.
Long story short, out of all of the configurations I had where h2 is enabled on the backend regardless of fe config the request fails into a retry loop and eventually bombs out across all haproxy versions. I managed to fix this but I don’t understand how haproxy as a client was susceptible to it. I tried 3 different version of curl in the testing process.
curl force h1 -> ingress controller <- return 302
curl force h2 -> ingress controller <- return 302
curl h1 -> upgraded to h2 ingress controller <- return 302
via haproxy version stated above
curl h1 -> haproxy force h1 be <- return 302 (no h2 configured)
curl h1 -> haproxy -> upgraded to h2 at ingress controller <- return 302
(h1 on fe, automatically upgraded without config to enforce otherwise)
curl h2 -> haproxy -> upgraded to h2 at ingress controller <- return 302
(h2 on fe, automatically upgraded at be without config to enforce otherwise)
curl h1 -> haproxy force h2 <- fail
curl h2 -> haproxy force h2 <- fail
Going direct no issue, letting the connection upgrade from h1 to h2 no issue. However h2 forced on the be immediate enter a retry loop and crash after 5.
So adding “http2-max-field-size: 8k” (default 4k) to the config in the ingress controller fixed the issue. I boiled this down to an HPACK framing issue early on but couldn’t prove it and didn’t have all of the tools to really inspect it so I was basically making an educated guess. Again I don’t understand how I have 3 scenarios where h2 is working but the 4th causes an issue and only from haproxy forward. Any insight into what haproxy is doing differently here would be invaluable.